The present invention relates to the improvement of hard disk testing apparatus.
In the conventional product quality test of magnetic recording type hard disks (hereinafter called "disk"), a test apparatus is provided with a pair of carriages diametrically opposing to each other which reciprocate in the radius direction of a disk, and a pair of upper and lower magnetic heads (hereinafter called "heads") are provided on each of the carriages so that the upper (front) side and the lower (back) side of the disk are simultaneously tested (measured).
One of the carriages is driven in a manner that its heads reciprocate in the inner half of the radius of the disk, and the other carriage is driven in a manner that its heads reciprocate in the outer half of the radius of the disk. Test signals are magnetically written in the disk surface with these heads, these signals or signals remaining after erasure are read with these heads again, and based on the reading results, several test items such as missing pulse error, extra pulse error, etc. are checked.
However, in the case of the above conventional disk test apparatus, the heads are fixed to the carriage using jigs a predetermined positions. But because of fixing errors, the predetermined separations of the heads may not be obtained. Therefore when both carriages are moved in predetermined distances, problems occur in which tracks around the border between the ranges covered by the heads mounted on one of the carriages and the heads mounted on the other carriage may be doubly tested or may not be tested. It is possible to avoid this kind of problems, i.e., duplication or omission of test, by carrying out micro adjustment based on measured separations of the heads. However, this type of manual micro adjustment is time-consuming.